528 ANNUAL. REPQRT OF THE Off. Doc. 



ORCHARD FERTILIZATION. 



Tiof. JNO. P. STEWART, Asst. Professor of Experimental Horticulture, Pennsylvania State 



College. 



In fruit production there are at least four factors that are es- 

 sential in securing maximum profits. Assuming that location and 

 varieties are proper, they are soil management, fertilization, pruning 

 and spraying. Each must be right. No one of them can be singled 

 out and made to carry the load of other left undone. Any one or 

 part of one neglected may become the crop-limiter of that orchard 

 and the extra care devoted to the others is lost. The truth of this 

 principle is emphatically shown in figures which we have recently 

 collected in a study of costs and profits in fruit growing. These 

 figures show that in the case of the apple net profits have actually 

 increased with expenditures up to more than |300 per acre for pro- 

 ducing and marketing the crop. Thus in fruit growing as elsewhere 

 one gets returns exactly in proportion to what he intelligently puts 

 into it. To increase this intelligence, we look into one of the most 

 complex of these production-factors, orchard fertilization. 



In the country as a Avhole, orchard fertilization is not being ne- 

 glected. The last census shows that the size of the orchard-fertiliza- 

 tion bill is about |2,000,000 per year. Fruit farms expended 30 

 fcents per acre for fertilizers as compared with 4 cent on hay and 

 grain farms, and 2 cents per acre on stock farms. Whether this 

 expenditure is being wisely made or whether it is sufficient is the 

 question. At the present time, we have no exact system of orchard 

 fertilization and little accurate data upon which one may be based. 



The systems of fertilization now in operation or recommended are 

 based on four things: (1) analyses of trees and their crops; (2) 

 general experience and observation; (3) orchard surveys; and (4) 

 experimental studies. Each has its strong and its weak points. 

 For example, analyses show that an acre of bearing apple trees takes 

 up about 55 lbs. of potash (K20) per year. But the fact that they 

 have this potash does not prove either that they must have it or 

 that its addition to the soil would secure any material response. In- 

 deed, the same analyses show the annual possession by the trees of 

 57 lbs. of lime per acre, and yet lime is not generally considered im- 

 portant in orchard fertilization. 



There are similar weaknesses, with the other sources of evidence. 

 General experience and observation fail because of their lack of checks 

 and their local application. Orchard surveys furnish the wide appli- 

 cation and are very valuable on this account, but they can not com- 

 pletely isolate any one factor, and they are confined to current prac- 

 tice. Experimental studies are confined to comparatively few trees 

 and soils, hence, must be more or less local. They also require long 

 periods of time. But in spite of defects, each of these sources of 

 evidence furnishes something and the final solution of the problem 

 will depend upon them all. 



In this discussion, we are concerned with the experimental evi- 

 dence. The apple is not an easy crop to deal with experimentally. 

 The difficulty of getting uniformity in soil and varieties over the 

 large areas required, the perennial nature of the plant with its re- 

 sulting food-storage for early spring growth, the continuous crop- 

 ping without chance for rotation, and the sensitive and fickle bearing 

 habit are a few of the difficulties that face the investigator. They 



